Well, if both people are making cities, but one is making a medieval city and another is making a more modern city, I wouldn't say those are two different versions. A medieval house is different from a modern one and the overall feel you get from both cities makes them different builds in my opinion. Personally I think that people should do as they please but be made very aware of what everyone is doing so they don't run off and build a town that's no different from another when they could've joined in with everyone else.
I intend to join sometime this week (maybe even today) but have a quick question: could there be a list of what addons or texture packs I need to get? Haven't really been on MC for a long time so can't remember where or what to download :S
We have a screenshot thread for mc https://www.gamingmasters.org/threads/just-another-screenshot-thread-minecraft.5114/page-24